CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Adoption of New Accounting Standard	Common Shares	Capital Surplus, Paid In	Retained Earnings	Retained Earnings Adoption of New Accounting Standard	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2018			316,885,808
Beginning balance at Dec. 31, 2018	$ 11,486,817		$ 1,669,392	$ 6,241,222	$ 3,953,974		$ (60,000)	$ (317,771)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2016-13 [Member]
Net Income	$ 916,572				916,572
Dividends on Common Stock	(685,979)				(685,979)
Dividends on Preferred Stock	(7,519)				(7,519)
Issuance of Common Shares (in shares)			11,980,000
Issuance of Common Shares	868,550		$ 59,900	808,650
Long-Term Incentive Plan Activity	3,434			3,434
Issuance of Treasury Shares (in shares)			1,014,837
Issuance of Treasury Shares	69,474			50,758				18,716
Capital Stock Expense	(16,296)			(16,296)
Other Comprehensive Income/(Loss), Net of Tax	(5,059)						(5,059)
Ending balance (in shares) at Dec. 31, 2019			329,880,645
Ending balance at Dec. 31, 2019	12,629,994	$ (1,514)	$ 1,729,292	7,087,768	4,177,048	$ (1,514)	(65,059)	(299,055)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,212,686				1,212,686
Dividends on Common Stock	(767,500)				(767,500)
Dividends on Preferred Stock	(7,519)				(7,519)
Capital Contributions from Eversource Parent	25,000
Issuance of Common Shares (in shares)			11,960,000
Issuance of Common Shares	949,660		$ 59,800	889,860
Long-Term Incentive Plan Activity	7,890			7,890
Issuance of Treasury Shares (in shares)			1,113,378
Issuance of Treasury Shares	71,888			50,812				21,076
Capital Stock Expense	(20,667)			(20,667)
Other Comprehensive Income/(Loss), Net of Tax	$ (11,352)						(11,352)
Ending balance (in shares) at Dec. 31, 2020	342,954,023		342,954,023
Ending balance at Dec. 31, 2020	$ 14,063,566		$ 1,789,092	8,015,663	4,613,201		(76,411)	(277,979)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,228,046				1,228,046
Dividends on Common Stock	(828,337)				(828,337)
Dividends on Preferred Stock	(7,519)				(7,519)
Long-Term Incentive Plan Activity	3,537			3,537
Issuance of Treasury Shares (in shares)			986,656
Issuance of Treasury Shares	68,364			49,913				18,451
Issuance of Treasury Shares for Acquisition of New England Service Company				29,401				8,650
Other Comprehensive Income/(Loss), Net of Tax	$ 34,136						34,136
Ending balance (in shares) at Dec. 31, 2021	344,403,196		344,403,196
Ending balance at Dec. 31, 2021	$ 14,599,844		$ 1,789,092	$ 8,098,514	$ 5,005,391		$ (42,275)	$ (250,878)